A 72-year-old woman with COPD (baseline PaCO₂ 50 mmHg) presents with acute exacerbation. She is drowsy and has cyanosis. Current labs: pH 7.25, PaCO₂ 70 mmHg, HCO₃⁻ 30 mEq/L, PaO₂ 55 mmHg on room air. What is the primary acid-base disorder and what is the acute change superimposed on her chronic baseline?